Strip line circulator wherein the branch arms have portions extending in a nonradial direction

ABSTRACT

Branch lines radially extend from a circular junction of an intermediate conductor on a ferri-magnetic disc and include one portion running circumferentially of the disc. This causes an increase in area with which the disc overlaps the branch lines while the lines are maintained relatively small in radial length resulting in a small-sized circulator low in center frequency.

Tlited ta Inventors Shojiro Nalrahara;

, Nobutalre Orime, both of lliarnallrura, Japan Appl. No. 879,760

Filed Nov. 25, 1969 Patented Nov. 2, 1971 Assignee Mitsubishi DenllriKabuslhilki Kaisha Chiyoda-lru, Tolryo, Japan Priority Nov. 213, 1968Japan 411/87 184 STlRlllP LllNlE CHRCULATOR WlllllERlEllN THE llBlRAN'ClHI AlRMS llllAVlE PORTIONS EXTENDING IN A NONNADKAIL DIRECTION10 Cllninas, 9 Drawing Figs.

[1.8. Ci 333/1.1, 333/84 M Tnt.Cll lhlOlp 1/32, H0 1 p 5/12 lFielill olisearch 333/1.1

[56] References Cited UNITED STATES PATIENTS 3,295,074 12/1966 Carr333/1.1 3,513,413 5/1970 Nakahara et al..... 333/].1 3,521,195 7/1970Bosma 333/l.1 3,522,555 8/1970 Hashimoto et al 333/l.l

Primary Examiner- Herman Karl Saalbach Assistant Examiner-Paul L.Gensler AttorneysRobert E. Burns and Emmanuel J. Lobato ABSTRACT: Branchlines radially ext-end from a circular junction of an intermediateconductor on a ferri-magnetic disc and include one portion runningcircumferentially 0f the disc. This causes an increase in area withwhich the disc overlaps the branch lines while the lines are maintainedrelatively small in radial length resulting in a small-sized circulatorlow in center frequency.

PATENTEU NW2 I97! SHEET 1 UF ,2

9 l PRIOR ART f =2.1 GHZ L0 L5 MAGNETIZING DC CURRENT in A ARMS III/IVEPORTIONS EXTENDING IN A NONRADIAIL DIII'IEGIION BACKGROUND OF THEINVENTION This invention relates to improvements in strip line-typecirculators.

The conventional type of stripline-type circulator widely employed hascomprised a ground conductor, an internal conductor composed of branchlines and their junction, and a plate of ferri-magnetic materialdisposed between the ground and internal conductors. The plate offerri-magnetic material has been applied with a magnetic field of directcurrent orthogonal to the main faces thereof. In the generalconfiguration of such circulators comprising the circular junction andthe branch lines radially extending at substantially equal angularintervals from the junction, the wider an area with which the plate offerri-magnetic material overlaps the branch lines the lower the centerfrequency of the circulator will be. If it is desired to provide such atype of circulator having its center frequency as relatively low as inthe order of l GHz. it has been required to sufficiently increase boththe diameter of the ferri-magnetic disc and the length of the branchlines leading to the disadvantage that the resulting circulator hasinevitably become large sized. Therefore, for use in apparatus requiredto be small sized as those equipped on artificial satellites, they havebeen unsuitable, and not so practical while being expensive.

SUMMARY OF THE INVENTION Accordingly, it is one object of the inventionto, provide a new and improved stripline-type circulator small indimension and cheap in manufacturing while being operated at relativelylow frequencies wherein the above-mentioned disadvantages of theconventional circulators are eliminated.

It is another object of the invention to provide a new and improvedstrip line type circulator which is small sized and operative over arange of relatively low frequencies by increasing the effectivemagnitude of distributed capacitance presented by branch lines radiallyextending at substantially equal angular intervals from their junctionwith no increase in radial length of the branch lines.

The invention accomplishes the above cited objects by the provision of astripline-type circulator comprising a ground conductor, an internalconductor including a plurality of branch lines and a junction thereof,the branch lines radially extending at substantially equal angularintervals from the junction, a body of ferri-magnetic material greaterin area than the junction and disposed between the ground and internalconductors and in overlapping relationship therewith, and magnet meansfor applying a magnetic field of direct current substantially orthogonalto and across the body of ferri-magnetic material, characterized in thatthe intermediate portions of the branch lines extend in a directionother than the radial direction in the region of the body offerri-magnetic material and in the same plane as the junction toincrease the effective area with which the body of ferri-magneticmaterial overlaps the branch lines.

If desired, that portion projecting beyond the junction of the body offerri-magnetic material may be replaced by a dielectric member in theform of a toroid integral to the body of ferri-magnetic material.

Conveniently, the turned portion of each of the branch lines may vary inlength to change the center frequency of the circulator whilemaintaining a constant area of that portion projecting beyond thejunction of the body of ferri-magnetic material.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will become readilyapparent from the following detailed description taken in conjunctionwith the accompanying drawings in which:

FIG. I is a fragmental plan view of a Wye-branched striplinetypecirculator constructed in accordance with the principles of the priorart;

FIG. 2 is a partly exploded perspective view of the conventional type ofstripline-type circulator;

FIG. 3 is a fragmental plan view of a Wye-branched striplinetypecirculator constructed in accordance with the principles of theinvention;

FIGS. da and db are fragmental plan views illustrating the conventionalstripline-type circulators equal in center frequency to the circulatorof the invention shown in FIG. 3;

FIG. 5 is a Smith chart and illustrating an input admittance as lookingfrom in each branch line of the circulator shown in FIG. db;

FIG. 6 is a chart similar to FIG. 5 but illustrating the circulatorshown in FIG. 4a;

FIG. 7 is a graphic representation of insertion losses of the presentdevice plotted against a magnetic field applied thereto; and

FIG. 8 is a fragmental plan view of a modification of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawingsand FIGS. 11 and 2 in particular, there is illustrated a wyebranchedstripline-type circulator constructed in accordance with the principlesof the prior art. The arrangement illustrated comprises an internalconductor of any suitable electrically conductive material generallydesignated by the reference numeral and including a circular centraljunction portion 12 called hereinafter a junction and a plurality ofbranch lines M in the form of strips radially extending at substantiallyequal angular intervals from the junction 12, and a disc 16 of anysuitable ferri-magnetic material such as garnet, disposed in concentricrelationship under the internal conductor 10.

Then the assembly thus formed is concentrically located within ametallic housing 118 of circular cross section and the branch lines 14are connected at their free ends to respective terminals 20 disposed atsubstantially equal angular intervals on the periphery of the housing 18as shown in FIG. 2. Another ferri-magnetic disc 16', as shown on theupper portion of FIG. 2, substantially identical to the ferri-magneticdisc 16 is concentrically disposed upon the internal conductor I0 and ametallic cover (not shown) is used to close the upper end of the housing18 as well as suitable holding the internal conductor 10 andferri-magnetic discs 16 and 116' in place within the housing 18. It willbe appreciated that the housing 118 and the cover form a conductorwhich, in turn, serves to sandwich or superimpose the ferri-magneticdiscs between the same and the internal conductor.

As shown in FIG. I, the garnet disc 16 having a diameter D radiallyprojects beyond the junction 12, having a diameter d, by a radiallength 1. Thus it will be appreciated that with an electric fieldapplied orthogonally to the main faces of the circulator and thereforebetween the internal conductor 10 and the ground conductor, as shown bythe arrow in FIG. 2, the electric field is weakly established on theperipheral portion in the form of an annulus having a radial width of lof the ferrimagnetic disc 16 whereby that portion disposed directlybelow each of the branch lines M of the disc to serves only as amatching element.

In FIG. 4b, wherein like reference numerals designate like componentscorresponding to those ilIustrated in FIG. I, is illustrated acirculator similar to that shown in FIG. I excepting that the disc 16 offerri-magnetic material and the junction 12 of the internal conductorII) have a common diameter d. When a magnetic field of II is applied tothe arrangement of FIG. db operated at its center frequency of 4.2 GHZ.,an input admittance as looking from each of the branch lines 14 isinductive with the reference plane located at its position spaced awayfrom the peripheral edge of the disc 16 by a distance of (Dd)/2, andsuch is illustrated in the chart of FIG. 5 wherein two orthogonal setsof circles represent conductance and susceptance componentsrespectively.

On the other hand, if the ferri-magnetic disc 16 of FIG. 4b having thediameter of d has snugly fitted thereon an annulus of ferri-magneticmaterial, such as garnet, having an inside diameter of d and an outsidediameter D such as shown in FIG. 1, then the resulting circulatorexhibits the effect equivalent to the loading of a capacitance andtherefore has an input admittance as shown in the chart of FIG. 6similar to that illustrated in FIG. 5. It has been found that theannulus of ferrimagnetic material may be replaced by an annulus havingthe same shape and composed of a dielectric material substantially equalin specific dielectric constant to the ferri-magnetic material for theannulus.

From the foregoing it will be understood that the larger the width orI=(Dd)/2 (see FIGS. 1 and 4a) of the above-mentioned annulus formed ofthe ferri-magnetic or dielectric material the lower the center frequencyof the circulator will be.

The invention is based upon the phenomenon just described andcontemplates to decrease the center frequency of the circulator byincreasing a length of each branch line with which the associatedferri-magnetic disc overlaps the individual branch line for the purposeof decreasing the center frequency of the circulator. That is, theinvention contemplates to increase the length l of the branch portion asshown in FIG. 1 without an increase in diameter of the ferri-magneticdisc.

-Referring now to FIG. 3 wherein like reference numerals designate likecomponents corresponding to those shown in FIG. 1, there is illustrateda stripline-type circulator constructed in accordance with theprinciples of the invention as above described. As in the arrangement ofFIG. 1, the circular junction portion 12 of the internal conductor 10 isdisposed in concentric relationship on the disc 16 of ferri-magneticmaterial such as garnet. The junction 12 has a diameter d and the disc16 has a diameter D greater than the diameter of the junction portion12. The junction 12 has a plurality of branch lines 14 in the form ofstrips radially extending at substantially equal angular intervals fromthe junction 12. At the periphery of the disc 16, the branch lines 14each are turned in one direction, for example in the clockwisedirection, as viewed in FIG. 3 of the disc to follow the periphery ofthe latter by a predetermined circumferentially extending arc lengthportion 1,. Then the branch lines 14 are again turned in the radialdirection of the disc 16. That is, a branch lines 14 each have the firstradial portion having a radial length of I, the circumferential portionhaving an arc length of 1,, and the second radial portion leading to theassociated terminal such as shown at 20 in FIG. 2.

Under these circumstances, it will be appreciated that that portion ofeach branch line 14 superposing the ferri-magnetic disc 16 increases inlength by an amount corresponding to the arc length I as compared withthe prior art type devices including the ferri-magnetic disc of the samediameter. This means that the ferri-magnetic disc 16 has effectivelyincreased in radius by an amount corresponding to the 1,. This providesa stripline-type circulator equivalent to a circulator including aferrimagnetic disc 16 increased in radius by about the I, as shown inFIG. 4a. Therefore the center frequency of the circulator can decreaseby a magnitude corresponding to this effective increase in radius of theferri-magnetic disc, while the overall dimension of the circulatorremains unchanged.

A stripline-type circulator such as shown in FIG. 3 had appliedperpendicularly thereacross a magnetic field of direct currentprogressively increased in strength with the center frequency f, of 2.1GI-Iz. Then it exhibited its insertion loss as shown in FIG. 7 whereinthe ordinate represents the insertion loss in decibels and the abscissarepresents a magnetizing direct current in amperes flowing through theassociated electromagnet device (not shown). The reference characters Lf and Lb designate the forward and reverse insertion losses.

It has been found that if the circumferential portion of each branchline 14 varies in arc length, the resulting center frequency can changeover a fairly wide range. For example, a circulator such as shown inFIG. 3 including the circumferential branch portions having a perimetriclength equal to one sixth the diameter of the associated ferri-magneticdisc has its center frequency decreased by a factor of 2 as comparedwith the conventional one including no circumferential branch lines withthe discs having the same diameter.

FIG. 8, wherein like reference numerals designate like componentssimilar to those shown in FIG. 3, illustrates a modification of theinvention. In FIG. 8, the ferri-magnetic disc 16 is equal in diameter tothe junction 12 and is integral with a dielectric member 18. Thedielectric member has the configuration of a toroid and thecircumferentially extending arc length portion of each branch line 14 issuperposed with the outer perimeter of the toroid.

It has been found that the present circulators are particularlyeffective for operating at frequencies under 1 GHz. This is because theferri-magnetic disc can overlap the branch lines with an area capable ofbeing selected to be sufficiently large while the radial length of eachbranch line is maintained relatively small.

While the invention has been illustrated and described in conjunctionwith a single preferred embodiment thereof it is to be understood thatvarious changes and modifications may be resorted to without departingfrom the spirit and scope of the invention. For example, as long asthose portions connected to the junction andthose portions projectingbeyond the ferri-magnetic disc of the branch lines are disposed inradially symmetric relationship with one another, those portionssuperposing the ferri-magnetic disc of the branch lines may assume anydesired configuration other than that previously described inconjunction with FIG. 3. Also it is to be understood that the inventionis equally applicable to any desired configuration other than thecircular one as previously described and with other than three branchlines.

What we claim is:

1. A stripline-type circulator comprising a ground conductor, aninternal conductor including at least three branch lines connectedtogether at a junction portion, said branch lines radially extending atsubstantially equal angular intervals from said junction portion, a bodyof ferri-magnetic material greater in area than said junction portionand disposed between said ground and internal conductors and inoverlapping relationship therewith, magnet means for applying a magneticfield of direct current substantially orthogonal to and across said bodyof ferri-magnetic material, and wherein intermediate portions of each ofsaid branch lines extend in a direction other than the radial directiona region overlying said body of ferri-magnetic material and in the sameplane as said junction portion to increase the effective area with whichsaid body of ferri-magnetic material overlaps said branch lines.

2. A stripline-type circulator as claimed in claim 1 wherein thatportion of said ferri-magnetic material projecting beyond said junctionportion is replaced by a dielectric member in the form of a toroidconnected integrally to said body of ferrimagnetic material.

3. In a stripline circulator having a planar conductor and a planar bodyof ferri-magnetic material superimposed on one side of said planarconductor; another planar conductor superimposed on the opposite side ofsaid planar body in overlapping relationship therewith having a centraljunction portion smaller in area than said planar body and having atleast three branch lines connected to and extending radially outwardlyfrom said junction portion in equidistantly circumferentiallyspaced-apart relationship; each of said branch lines having a firstportion extending in a first radial direction radially outwardly fromsaid junction portion a distance no greater than the radial extent ofsaid planar body, a second portion extending in a direction other than aradial direction with respect to said junction portion and overlyingsaid planar body, and a third portion extending radially outwardly fromsaid junction portion in a radial direction different than said firstradial direction.

d. A stripline circulator according to claim 3; wherein said first,second and third portions of each branch line have substantially thesame cross-sectional configuration.

5. A stripline circulator according to claim 3; wherein said secondportion of each branch line extends in the same direction as that of theperimeter of said planar body.

6. A stripline circulator according to claim 3; wherein saidfirst-mentioned planar conductor, said planar body and said anotherplanar conductor are all concentrically disposed in layeredrelationship.

7. in a stripline circulator having a planar conductor and a planar bodyof t'erri-magnetic material superimposed on one side of said planarconductor; another planar conductor superimposed on the opposite side ofsaid planar body having a central junction portion equal in area to thatof said planar body and having at least three branch lines connected toand extending radially outwardly from said junction portion inequidistantly circumferentially spaced-apart relationship; a dielectricmember composed of dielectric material surrounding the periphery of saidplanar body; and wherein each of said branch lines has a first portionextending in a first radial direction radially outwardly from saidjunction portion a distance no greater than the radial extent of saiddielectric member, a second portion extending in a direction other thana radial direction with respect to said junction portion and overlyingsaid dielectric member, and a third portion extending radially outwardlyfrom said junction portion in a radial direction different than saidfirst radial direction.

8. A stripline circulator according to claim 7; wherein said first,second and third portions of each branch line have substantially thesame cross-sectional configuration.

9. A stripline circulator according to claim 7; wherein said secondportion of each branch line extends in the same direction as that of theperimeter of said dielectric member.

10. A stripcirculator according to claim 7; wherein said first-mentionedplanar conductor, said planar body, said dielectric member and saidanother planar conductor are all concentrically disposed in layeredrelationship.

2. A stripline-type circulator as claimed in claim 1 wherein thatportion of said ferri-magnetic material projecting beyond said junctionportion is replaced by a dielectric member in the form of a toroidconnected integrally to said body of ferri-magnetic material.
 3. In astripline circulator having a planar conductor and a planar body offerri-magnetic material superimposed on one side of said planarconductor; another planar conductor superimposed on the opposite side ofsaid planar body in overlapping relationship therewith having a centraljunction portion smaller in area than said planar body and having atleast three branch lines connected to and extending radially outwardlyfrom said junction portion in equidistantly circumferentiallyspaced-apart relationship; each of said branch lines having a firstportion extending in a first radial direction radially outwardly fromsaid junction portion a distance no greater than the radial extent ofsaid planar body, a second portion extending in a direction other than aradial direction with respect to said junction portion and overlyingsaid planar body, and a third portion extending radially outwardly fromsaid junction portion in a radial direction different than said firstradial direction.
 4. A stripline circulator according to claim 3;wherein said first, second and third portions of each branch line havesubstantially the same cross-sectional configuration.
 5. A striplinecirculator according to claim 3; wherein said second portion of eachbranch line extends in the same direction as that of the perimeter ofsaid planar body.
 6. A stripline circulator according to claim 3;wherein said first-mentioned planar conductor, said planar body and saidanother planar conductor are all concentrically disposed in layeredrelationship.
 7. In a stripline circulator having a planar conductor anda planar body of ferri-magnetic material superimposed on one side ofsaid planar conductor; another planar conductor superimposed on theopposite side of said planar body having a central junction portionequal in area to that of said planar body and having at least threebranch lines connected to and extending radially outwardly from saidjunction portion in equidistantly circumferentially spaced-apartrelationship; a dielectric member composed of dielectric materialsurrounding the periphery of said planar body; and wherein each of saidbranch lines has a first portion extending in a first radial directionradially outwardly from said junction portion a distance no greater thanthe radial extent of said dielectric member, a second portion extendingin a direction other than a radial direction with respect to saidjunction portion and overlying said dielectric member, and a thirdportion extending radially outwardly from said junction portion in aradial direction different than said first radial direction.
 8. Astripline circulator according to claim 7; wherein said first, secondand third portions of each branch line have substantially the samecross-sectional configuration.
 9. A stripline circulator according toclaim 7; wherein said second portion of each branch line extends in thesame direction as that of the perimeter of said dielectric member.
 10. Astripcirculator according to claim 7; wherein said first-mentionedplanar conductor, said planar body, said dielectric member and saidanother planar conductor are all concentrically disposed in layeredrelationship.